iOS 10.3 as well as iOS 11.2 - multiple devices. The DVR will replay just fine.
Most likely cause is that your internet/wifi speed can not keep up with the needed data delivery of the stream app. Test your speed here:
it happens both at home with a 75mbps connection and at work with a 1gbps connection (with no QOS in play). so... no, that isn't it.
Those are wired speeds, aren't you using wifi?
please see this post and send that Official Employee a private message (directions in post).
edit: the link didn't work.. http://forums.xfinity.com/t5/Stream-TV-App/Xfinity-Stream-TV-app-download-failures/td-p/3003867
locking this thread.